Sulfonation of fatty acids



June 6, 1967 N. D. GORDON SULVFONATION OF FATTY ACIDS Filed Nov. 27,1963 mmhfu O...

INVENTOR: NORMAN D. GORDON W an;-

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24k Dumb- United States Patent ware Filed Nov. 27, 1963, Ser. No.326,432 5 Claims. (Cl. 260400) This invention relates to the sulfonationof fatty acids, and more particularly to continuous sulfonation of fattyacids using 100% sulfur trioxide.

The advantages of using 100% sulfur trioxide have been recognized, butbecause of problems associated with the use of concentrated trioxide,the processes heretofore used have employed extremely diluted trioxidein air, thereby requiring expensive auxiliary equipment andinstrumentation. Any attempts to sulfonate fatty acids using 100% sulfurtrioxide vapor have been unsuccessful, the product being unsatisfactoryas to quality and failing to have an acceptable color. In such priorattempts, diluted sulfur trioxide vapor was atomized to avoid localcharring and overheating due to the high exothermic heat generated, butin all such cases, the local charring and overheating could not beavoided and the product failed to have an acceptable color.

An object of the present invention is to provide a process overcomingthe above-described difiiculties and eifectively sulfonating fatty acidswith 100% sulfur trioxide and with substantial yields of a high qualityproduct. A further object is to provide a continuous process in whichthe fatty acids are sulfonated with 100% sulfur trioxide, Other specificobjects and advantages of the invention will appear as the specificationproceeds.

I have discovered that if a liquid fatty acid, preferably in thepresence of its solvent, is atomized and the resulting mist of particlesdischarged through sulfur trioxide vapor so that the contact time isvery brief, local concentrations of sulfur trioxide are avoided andthere is a minimum of local overheating and product degradation.Further, the process may be operated continuously with yields in therange of 80% and higher, while obtaining a high quality product withgood color.

In one embodiment of the invention, a fatty acid, preferably in asolvent therefor, is atomized, and the resulting fine particles passedthrough a confined body of sulfur trioxide vapor, the sulfonated fattyacid being collected and processed for the separation of the solvent andthe subsequent purification of the sulfonated product. In the foregoingprocess. I prefer to recycle a portion of the liquid product in theatomization and discharge steps in which contact is made with the sulfurtrioxide vapor.

In a preferred operation, the fatty acid in its solvent is heated to atemperature in the range of about l25l60 F., and the liquid atomizedwithin a chamber containing sulfur trioxide vapor, the fine fatty acidparticles being discharged at a high velocity through the vapor so thatcontact time is very short (fraction of a second or so). Any means foratomizing the liquid fatty acid may be employed since it is onlynecessary to break up the liquid into a mist of particles and to movethe particles at a substantial speed through the sulfur trioxide vaporbody.

The sulfur trioxide vapor may be formed by any suitable means. Ifdesired, the sulfur trioxide may be vaporized in a steam heatedvaporizer, an electric vaporizer heater, or any other suitablevaporizer. The sulfur trioxide may then be introduced into a chamber soas to form a body of vapor and the fatty acid solution may be dischargedas a mist so as to pass through the body of vapor.

Any suitable solvent may be employed which will main- 2 tain the fattyacid in a liquid state at the reaction temperature. The use of solventwith the fatty acid depends upon the melting point and solubility of theacid so that the solvent will assure a liquid fatty acid state at thereaction tempertaure. A further purpose of the solvent is to preventlocal overheating and subsequent darkening of the fatty acid and thereaction product. Perchloroethylene, carbontetrachloride, and otherknown solvents may be employed.

The fatty acid may be any fatty acid which can be liquefied for theatomization step and preferably comprises fatty acids having from 12 to22 carbon atoms. The process has been particularly effective in the sul-'onation of stearic, palmitic, lauric and myristic acids.

While various types of atomizing devices and equipment may be employed,a specific form of apparatus which is illustrative is set out in theaccompanying drawing in which the apparatus is diagrammatically shown.

Fatty acid, dissolved in a solvent, is heated preferably by a steam coilin a feed tank and fed by pump and through a flow control (Rotameter) toa rotor casing 12 where the liquid acid is discharged between spaceddisks forming a rotor head 16. The rotor head is driven by motor 14 andthe liquid enters the channel of the rotor mechanism through the line15. The sulfur trioxide vapor is introduced through line 17 into adistributor 18 having openings through which the vapor is discharged tosub stantially fill the upper portion of the closed shell 19. The sulfurtrioxide vapor forms a body about the rotor head 16 as indicated by thearrows 20, and the vapor exits through an outlet pipe 21 having itsopening above the liquid acid body 22. The liquid mist, on emission fromthe rotor head 16, passes through the trioxide vapor and impinges on thewalls of the shell 19, from which it flows to the liquid body 22therebelow. The velocity of the liquid mist is such that less than asecond is required to impinge it upon the shell.

The exothermic heat of reaction is removed by means of a cooling waterjacket 23 extending about the shell 19. If desired, a thermocouple maybe carried by the shell 19 for indicating the outside shell temperature.Liquid may be recycled from the liquid body 22 through the line 24 bymeans of pump 25 and through flow control 26 back to the feed line 15.

The reacted product may be withdrawn through outlet 27 and pipe 28 tothe aging tank which is preferably maintained at a reaction temperature,the product being held for an additional period such as one hour beforetransferring it to the crystallizer. The sulfonated fatty acid is cooledin the crystallizer and may be reduced in solubility to promotecrystallization by the introduction of petroleum ether (Skelly Solv), orlike solvent. Seeding may be accomplished by the addition of crystallinematerial to promote crystallization of super-cooled solutes. From thecrystallizer the product may be passed to a filter (not shown), washedwith Skelly Solv F until free of solvent, and then vacuum dried. It will-be understood that such purification or final processing steps may bevaried substantially, depending upon the product desired.

The yield is found to be improved substantially by the recycling of acidfrom the body 22, and I prefer to recycle at a ratio of 4 or 5 to 1 inthe apparatus described .above, best results being obtained when therecycle ratio of the reaction mass (including the weight percent ofsolvent to feed is approximately 4.5 to 1 when employing a single rotorreaction stage, as illustrated in the drawing. Yields of from about 72to 83 weight percent, with product colors ranging from Gardner 10 to 13(20 percent in isopropanol) were obtained.

The aging at reaction temperatures was found to improve yields in bothbatch and continuous operations and for periods of about /2 to 3 hours,best results being obtained at about 1 hour.

While in the apparatus described above, a single rotor was employed, itwill be understood that multiple rotor stages may be used for increasingthroughout and for shortening the operation periods.

Specific examples illustrative of the process may be set out as follows:

EXAMPLE I A 21 percent solution of commercially pure stearic acid inperchloroethylene was heated by a steam coil in the tank, as shown inthe drawing, to a temperature of about 132 F. and discharged through therotor head 16 in the form of a fine mist at a high velocity. Sulfurtrioxide vapor in a concentration of 39 percent in air and at atemperature of about 92 F. was discharged at the rate of 0.10 pound perminute into the shell 19, as shown in the drawing, the shell having atemperature of about 103 F. The vented gases from the shell had atemperature of 114 F.

The liquid feed and solvent were introduced into the atomizer or rotorhead 16 at a rate of 1.65 pounds per minute, and liquid product frombody 21 was recycled at a ratio of 6.7 to 1. The temperature in thereceiver or aging tank 29 ranged between 140 and 158 F. and held a totalweight of 182 pounds. The digestion temperature was approximately 135 F.The crystallization temperature was about 90 F. and the yield was 81% byweight of theory. The assay results were as follows:

Assay A.V. total 306 A.V. SO I-I 160 A.V. COOH 146 GA (20%) color 15EXAMPLE II The process was carried out as described in Example I exceptas to the following conditions:

The feed rate for the fatty acid and solvent was 1.62 pounds per minuteat a temperature of 142 150 F. the sulfur trioxide vapor was introducedat the rate of 0.10 pound per minute and at a concentration of 100percent S The vapor temperature was 113 F. The shell temperature was114-116 F. The temperature of the vent gases was 104-100 F. The ratio ofthe recycled feed was 46 to l, the recycled product having a temperatureof 118-122 F. The temperature of the product in the receiver or agingtank was 142156 F., and the total weight was 178 pounds. The digestiontemperature was 135 F., and the crystallization temperature 76 F. Theyield was 78.9% by weight, and the color was Gardner 12.

EXAMPLE III The operation was carried out as described in Example Iexcept that the feed rate was increased to 2.53 pounds per minute. Thesulfur trioxide feed rate was 0.157 pound per minute. The sulfurtrioxide concentration was 100 percent and the temperature was 113 F.The shell temperature was 114 F., and the temperature of the vent gaseswas 105110 F. The recycle ratio was 4.5 to 1 of the reaction mass(including solvent) to feed, the temperature of the recycled productbeing 125128 F.

The weight of the total material in the aging tank was 187 pounds,having a temperature of 125128 F. The digestion temperature was 140 F.The crystallization temperature was 75 F. The yield was 72.2 percent by4 weight, and the color was Gardner (20 percent in isopropanol) 11-12.

EXAMPLE IV The process was carried out as described in Example I exceptthat the feed rate of the liquid acid and solvent was 2.56 pounds perminute at a temperature of 148 158 F. The sulfur trioxide was percent inconcentration and was fed at a rate of 0.171 pound per minute, having avapor temperature of 113 F. The shell had a temperature of 114 F., andthe vent gases had a temperature of -1 10 F. The recycle ratio was 4.47to 1, the recycled product having a temperature of 130150 F. There was atotal of 184 pounds in the receiver (aging tank) at a temperature of122125 F. The digestion temperature was 138 F., and the crystallizingtemperature 80 F. The yield was 72.2 weight percent, and the color wasGardner (20 percent in isopropanol) 1213.

While in the foregoing specification I have set forth illustrativeoperations in considerable detail for the purpose of illustrating theinvention, it will be understood that such detail or details may bevaried Widely by those skilled in the art without departing from thespirit of my invention.

I claim:

1. Ina process for sulfonating saturated, unsubstituted fatty acidshaving from about 12 to 22 carbon atoms, the steps of introducing into aconfined zone a body of 100 percent sulfur trioxide vapor in the upperportion of said zone, dissolving a feed fatty acid in a solvent to forma free-flowing liquid, atomizing said liquid into mist particles,passing said particles through and beyond said vapor body, andcollecting said particles in a liquid body below said vapor body.

2. The process of claim 1 in which the fatty acid is selected from agroup consisting of stearic, palmitic, lauric and myristic acids.

3. The process of claim 1 in which said liquid is recycled .at a ratioof about 4 to 5 parts of the recycled liquid to one of said feed acid.

4. The process of claim 1 in which liquid product is withdrawn from saidliquid body and aged in a reaction zone at a temperature of about 150 F.for about onehalf to three hours.

5. A process for sulfonating saturated, unsubstituted fatty acids havingfrom 12 to 22 carbon atoms in their hydrocarbon radical in which a fattyacid is dissolved in a solvent to form a free-flowing liquid andcontacted with sulfur trioxide vapor, characterized in that the sulfurtrioxide vapor is maintained in a substantially uniform body in an upperportion of a reaction zone and said fatty acid and solvent are atomizedinto mist particles and the particles passed through said vapor body andcollected free of said vapor in a liquid body below said vapor body inthe reaction zone.

References Cited UNITED STATES PATENTS 2,523,582 9/1950 Mattson 260-686X 2,768,199 10/1956 Luntz et al. 260686 X FOREIGN PATENTS 326,815 3/1930Great Britain.

ALEX MAZEL, Primary Examiner. JOSEPH P. BRUST, Examiner. A. H. SUTTO,Assistant Examiner.

1. IN A PROCESS FOR SULFONATING SATURATED, UNSUBSTITUTED FATTY ACIDSHAVING FROM ABOUT 12 TO 22 CARBON ATOMS, THE STEPS OF INTRODUCING INTO ACONFINED ZONE A BODY OF 100 PERCENT SULFUR TRIOXIDE VAPOR IN THE UPPERPORTION OF SAID ZONE, DISSOLVING A FEED FATTY ACID IN A SOLVENT TO FORMA FREE-FLOWING LIQUID, ATOMIZING SAID LIQUID INTO MIST PARTICLES,PASSING SAID PARTICLES THROUGH AND BEYOND SAID VAPOR BODY, ANDCOLLECTING SAID PARTICLES IN A LIQUID BODY BELOW SAID VAPOR BODY.